This one, it appears, has done it. Over the course of the last three months the Celtics have dealt with a string of injuries that would have knocked most teams sideways. First it was All-Star point guard Rajon Rondo, out for the year with an ACL tear. Then it was rookie power forward Jared Sullinger, who is done for 2013 because of back surgery. Just for a little insult to go with that injury, even bench guard Leandro Barbosa suffered a season-ending knee injury and was shuttled off to the Wizards at the trade deadline.

Even through those setbacks, the Celtics were able to thrive. But now they’re left to cope with a damaged Kevin Garnett, and of all the players they could ill afford to lose for a period of time, Garnett is on top of the list.

Leandro Barbosa played inspired basketball for the Boston Celtics before he went down with a knee injury and was traded to the Washington Wizards. (AP Photo)

On Monday, coach Doc Rivers told reporters before the Celtics’ practice that the foot injury Garnett suffered two games ago against Dallas was probably not going anywhere. Full results of the MRI on the foot were not available, but Rivers seemed assured that Garnett would be back at some point—but that point is undetermined.

“Can he miss four or five games?” Rivers wondered, according to the Boston Globe. “Yeah, that’s probably possible. I don’t know that but to me (season-ending) is not a concern. He hurt his foot in that Dallas game. Unless something crazy happens in the MRI that I can tell you the first look, they didn't see (something serious). At the end of the day, he may miss some games. We’re going to err on the right side, whatever they decide. If they give me an option of you can play him every third game or give him two weeks rest, I can tell you right now I am going to say two weeks rest, if it’s my decision.”

Team president Danny Ainge did say that he expected Garnett to need those two weeks to let the inflammation in his foot heal. Ainge also added that he thought the injury happened in the New Orleans game last Wednesday, and just got worse during the Dallas game.

This is rough news for a Boston team heading into a date that, as little as nine days ago, was highlighted on the calendar of all Celtics fans—the Knicks are slated to come to the TD Garden on Tuesday. Back on March 16, the Celtics were 36-29 and entertaining thoughts of winning the Atlantic Division, a goal that appeared unattainable when Rondo got injured at the end of January. But after beating Charlotte two Saturdays ago, the Celtics were just 3.0 games behind the Knicks, with Tuesday’s game to be followed by a game in New York this Sunday. A pair of wins in those games would draw the Celtics easily within striking distance, and give them the tiebreaker edge.

But the Celtics couldn’t catch a break with Garnett’s health—he suffered a strained stomach muscle, then was out with an illness when Boston narrowly lost at home to the Heat. Now, it’s the foot injury.

Even with Garnett playing, the Celtics got their three-game road trip off to an awful start, and wound up losing all three. The roster is absurdly thin on big men, with Brandon Bass and Chris Wilcox the only legitimate, healthy NBA-caliber power forwards on the roster.

Four straight losses combined with four straight wins for the Knicks, have moved the Celtics to 6.5 games out of first place. Now they’re just fighting to move up a bit in the Eastern Conference standings, where they’re stuck with the No. 7 seed. They’re only 2.0 games ahead of Milwaukee, which holds the No. 8 seed.

You have to give the Celtics credit for the injuries they’ve had to handle this year. But with Garnett out for any extended period, the free-fall that the team is in will be tough to break. It’s only a matter of how long it lasts and how deep it gets.